Chap. X. PREPOTENT POLLEN. 395 



green laciniated leaves; and of the 325 seedlings 

 raised from the purple-green variety, 165 had white- 

 green and 160 purple-green leaves. Of the 466 seed- 

 lings raised from the white-green variety, 220 had 

 purple-green and 246 white-green leaves. These case? 

 show how largely pollen from a neighbouring variety 

 of the cabbage effaces the action of the plant's own 

 pollen. We should bear in mind that pollen must be 

 carried by the bees from flower to flower on the same 

 large branching stem much more abundantly than 

 from plant to plant ; and in the case of plants the 

 flowers of which are in some degree dichogamous, 

 those on the same stem would be of different ages, and 

 would thus be as ready for mutual fertilisation as the 

 flowers on distinct plants, were it not for the prepotency 

 of pollen from another variety.* 



Several varieties of the radish (Raphanus sativus), 

 which is moderately self-fertile when insects are ex- 

 cluded, were in flower at the same time in my garden. 

 Seed was collected from one of them, and out of twenty- 

 two seedlings thus raised only twelve were true to their 

 kind.f 



The onion produces a large number of flowers, all 

 crowded together into a large globular head, each 

 flower having six stamens ; so that the stigmas receive 

 plenty of pollen from their own and the adjoining 

 anthers. Consequently the plant is fairly self-fertile 

 when protected ' from insects. A blood-red, silver, 

 globe and Spanish onion were planted near together; 



* A writer in the ' Gardeners' ling was true to its kind, and 



Chronicle' (1855, p. 730) says several closely resembled rape, 



that he planted a bed of turnips t Duhamel, as quoted by God- 



(Brassica rapa) and of rape (B. ron, ' De l'Espece,' torn. i. p. 50, 



napus) close together, and sowed makes an analogous statement 



the seeds of the former. The with respect to this plant, 

 result was that scarcely one seed" 



